Short answers, pulled from the story.
Star Wars: The High Republic is set roughly 500 to 100 years before the events of the Skywalker Saga, during a golden age when the Galactic Republic was expanding into the Outer Rim and the Jedi Order was at its most powerful and diverse.
Charles Soule wrote Light of the Jedi, the opening novel of Star Wars: The High Republic, published on the 5th of January 2021. Soule was one of five founding authors who developed the initiative at Skywalker Ranch in September 2018.
The Great Disaster is the inciting event of Star Wars: The High Republic, depicted in Light of the Jedi. A ship is destroyed while traveling through hyperspace, sending debris that threatens to destroy an entire star system.
The Nihil are the primary antagonists of Star Wars: The High Republic, described by the project's creators as "space Vikings." Marchion Ro leads the organization, and three officers called Tempest Runners hold the second-highest rank beneath him.
Star Wars: The High Republic consists of three phases. Phase I, called Light of the Jedi, ran from January 2021 to February 2022. Phase II, Quest of the Jedi, began in October 2022. Phase III, Trials of the Jedi, started in November 2023.
Light of the Jedi debuted at number one on The New York Times hardcover fiction bestseller list and held a spot for four weeks. A Test of Courage debuted at number two on the Times middle-grade list, and Into the Dark reached number one on the young adult hardcover list.